This invention relates to a method and apparatus for spraying fluids such as liquids, particulate solids, and slurries. More particularly, this invention is directed to a method and apparatus for spraying a fluid onto a surface which is disposed above, below or laterally to the spray apparatus.
Spraying is a known technique for applying a liquid or a liquid containing a solid onto a surface. Spraying is a common technique used for applying paint and other protective coatings onto metal, wood and other surfaces. Cleaning agents and other like materials are also often applied by spraying onto a surface. In addition, in the food industry spraying is a common technique for applying coatings onto various products during the process of manufacture. It is therefore not surprising that in view of this widespread use of spraying for applying liquids, solids, and slurries onto surfaces that there are many types of equipment that are used to carry out the various spraying techniques.
Some spraying techniques use a pressurized gas such as air or carbon dioxide to propel the material being sprayed toward and onto a surface. In these techniques the pressurized gas will also serve to deagglomerate the material that is being sprayed. The technique known as airless spraying is also used to apply a material onto a surface. In these techniques the material to be applied is pressurized and ejected through a nozzle. The nozzle is usually a small opening through which the material being sprayed is forced. These are the most commonly used general techniques for spraying fluids onto a surface.
The present discovery is directed to a spray technique for applying substances onto a surface, and particularly the surface of a food item during the process of manufacture. Although the present device can be used to apply the sprayed material in the form of droplets or a discontinuous mist, it is particularly useful in the coating of food items wherein it is desired to coat the item using a continuous curtain of sprayed material. Such processes are also known as enrobing. In these processes a continuous curtain of the fluid is directed toward the material to be coated. The material to be coated will usually be moved across the path of the curtain, thereby becoming coated with the sprayed material. However, it is also possible to keep the material being coated stationary and to move the nozzle which is delivering the coating. In either embodiment a material can be coated with a curtain of a substance.
Since new food products are being constantly developed, new techniques must be developed in order to economically produce these products Many of these new products use various flavored coatings in order to produce different tastes. More products are being coated for this purpose. The coatings which are used range from liquids such as oils, liquids which have various dissolved substances such as flavorants, liquid-solid combinations in the form of slurries, and solids such as spices and flavorants. The ideal is to have spray equipment which can handle liquids, solids and liquid-solid mixtures. The present spray device can be used with these various materials. In addition, the present spray device can be used in essentially any orientation. That is, this spray device can apply a material downwardly, laterally or upwardly. In this way the top, sides and/or the bottom can be readily coated.
Various apparatus and methods have been used in the past to apply sprayed materials onto edible products. In U.S. Pat. No. 2,856,870 globules of fat are applied using a spray technique. The nozzles are directed downwardly for the ejection of the fat in divergent jets or sprays onto a dough sheet surface below. The fat is heated to maintain it at a liquid consistency. This would be a conventional spraying of a liquid onto a solid.
In U.S. Pat. No. 3,057,730 a plurality of spray batteries spray shortening and water onto a surface which also contains flour. By the successive deposits of shortening, water and flour there is constituted a batter which is subsequently baked into an edible product. The shortening and water that are sprayed downwardly onto the surface are sprayed in an atomized form. The shortening and water are atomized through the use of a gear pump.
U.S. Pat. No. 3,120,198 discloses the application of an oil onto biscuits and related food products. In this technique the oil that is to coat the dough is pumped to nozzles which coat the dough which is disposed below the nozzles. The nozzles are also moved in a reciprocating motion in order to get a uniform coating of the oil on the dough.
U.S. Pat. No. 3,158,486 discloses having one or more conventional spray units disposed over a food product for treating the food product with a liquid. After being treated with the sprays of oil and water the product is then baked in an oven.
U.S. Pat. No. 3,167,032 discloses the use of a hopper device for providing a coating onto a food product which is disposed below the hopper. In this technique a solid within the hopper will be dropped downwardly onto the food product. This hopper can have the exit designed such that the solid is delivered only to certain parts of the food product which moves below the hopper. This hopper solely uses gravity to deliver the solids onto the food product.
U.S. Pat. No. 3,632,356 discloses an apparatus for coating articles with a viscous liquid in such a way the articles, but not the tops thereof. This device uses a curtain of the coating material to coat the object. The tops are free of any coating, or partially free of any coating, by providing an interruption in the curtain in alignment with the object as it moves through the curtain area. This patent describes a conventional curtain enrobing technique for coating.
U.S. Pat. No. 4,246,838 discloses an apparatus and method for slitting the upper surfaces of a plurality of dough pieces which are on a conveyor. Along with slitting there are spray nozzles which deliver a spray of a fluid into the area of the newly formed slit. This oil is delivered by means of a conventional spray technique.
U.S. Pat. No. 4,283,012 discloses a self-cleaning nozzle. This nozzle is specially adapted for spraying food ingredients. The nozzle which is disclosed can be used to form a curtain of sprayed material which is used to enrobe the object which is disposed below the spray nozzle. This spray nozzle consists of an inner opening through which the enrobing material is pumped and surrounded by an outer opening through which a current of air passes. The combination of the air and the pumped material creates a curtain of the material to be applied. As noted in this patent, nozzles of this type are very susceptible to clogging. There apparently is no way to keep them from clogging. This patent is directed to a technique for periodically cleaning out the nozzle while it is in use. However, each time the nozzle goes through a cycle of being cleaned, the curtain is interrupted. If, at the same time the from being passed under the spray nozzle, some of this product will not be properly coated.
U.S. Pat. No. 4,456,446 discloses a method for applying oil onto portions of a dough. In this patent there is disclosed a technique for providing a downward indentation in a piece of dough and for applying oil into this downward indentation. The device for applying the oil includes a means for providing the oil in an intermittent manner.
These patents disclose various techniques for applying a liquid or a solid to a surface. However, the nozzle that produces a curtain of a material is highly susceptible to clogging. As a result, the curtain has to be interrupted periodically so that a nozzle opening cleaning means can move into the nozzle area to clear the nozzle. While the various techniques disclosed in these various patents are effective in various coating operations, the present nozzle, and the means of applying fluids to a surface, have many advantages. One advantage is that it is non-clogging. Another is that, in use to form a curtain, an air source is not also required. Yet another advantage is that the present spray device can be used in any orientation. That is, it can deliver the coating material downwardly, laterally or upwardly. This provides for considerable versatility in the coating of a surface with a material. In addition, the spray devices are easily and readily interchangeable. This is important when there is to be a change in the product to be coated. The spray devices can be quickly changed to accommodate such production changes.